[robertjschu]

3 phase motor 1hp

[jcaron2]

In theory, no you don't. You can use a 3-pole switch (triple pole single throw TPST) to simultaneously open/close all three phases. However, you should also make sure to have over-current protection (i.e. fuses or breakers) in all three legs. Bear in mind that the resulting switch acts like an on/off toggle, not a push-button start/push-button stop like a normal 3-phase starter.

You could also add triple pole double throw (TPDT) switch (or use a triple pole triple throw to begin with) to be able to reverse the motor direction, in addition to turning it on or off.